1. Field of the Invention
The present invention generally relates to an agent for treating waste water and to a waste water treatment system, and more particularly, the present invention relates to an agent for treating waste water containing non-biodegradable dimethylsulfoxide and to a waste water treatment system which utilizes the agent.
A claim of priority is made to Korean Patent Application No. 2002-43350, filed on Jul. 23, 2002, and entitled “WASTE WATER TREATING AGENT AND WASTE WATER TREATING SYSTEM”, which is hereby incorporated by reference in its entirety.
2. Description of Related Art
Waste water has conventionally been treated by an activated sludge process which is a kind of biological waste water treatment process. However, such a process is generally ineffective in decomposing toxic dimethylsulfoxide contained in the waste water, and accordingly, non-decomposed dimethylsulfoxide is usually released into rivers after being sufficiently diluted so as to comply with environmental regulations. Accordingly, the waste water treatment efficiency is adversely impacted because the toxicity of dimethylsulfoxide causes shock to microorganisms, called microbe shock.
Dimethylsulfoxide is used in the fabrication of liquid crystal displays (LCDs). Generally, dimethylsulfoxide is produced in such a way that heated methanol gas reacts with hydrogen sulfide to generate dimethysulfide, and then the dimethylsulfide reacts with nitrogen to produce dimethylsulfoxide. The dimethylsulfoxide produced by the foregoing process has a double reactivity characteristic, so that it can be oxidized by reacting with a strong oxidizing agent or reduced by reacting with a strong reducing agent. The reduced dimethylsulfoxide exhibits toxicity, causing microbe shock as mentioned above. As explained below, the conventional biological waste water treating process is not well-suited for treating waste wafer containing dimethylsulfoxide.
FIG. 1 illustrates a conventional dimethylsulfoxide treatment system employing a typical biological waste water treatment process.
Referring to FIG. 1, dimethylsulfoxide contained in industrial effluent is gathered together to a water tank 20 via a dimethylsulfoxide tank 10, and then transferred to an aeration tank 30 via a connection pipe 60. In the aeration tank 30, organic substances contained in the waste water are decomposed by microorganisms such as activated sludge. Then, the waste water is transferred to a sedimentation tank 40 and the organic substances and dimethylsulfoxide are settled to the bottom of the sedimentation tank 40. Then, a portion of treated waste water in the sedimentation tank 40 is transferred to a treated water tank 50 and the remainder is returned to an aeration tank 30 so as to dillute the concentration of dimethylsulfoxide.
In the system of FIG. 1, since dimethylsulfoxide is almost non-biodegradable, the only treatment realized with respect to the dimethylsulfoxide is dilution of the dimethylsulfoxide.
Further, only demand oxygen (DO) and mixed liquor suspended solid (MLSS) concentration in the aeration tank 30 are controlled as management factors of the conventional biological waste water treatment system. The conventional system is not able to effectively deal with the lowered efficiency of the waste water treatment and microbe shock caused by toxicity of the reduced dimethylsulfoxide.
In fact, after operating the conventional waste water treatment system in FIG. 1 to treat waste water containing dimethylsulfoxide, it is observed that the quality of the treated waste water is degraded due to the lowered waste water treatment efficiency, thus making it difficult to realize a water quality in compliance with environment standards.